Assessment of Storm Surge History as Recorded by Driftwood in the Mackenzie Delta and Tuktoyaktuk Coastlands, Arctic Canada

Roger F Macleod,Scott R Dallimore

doi:10.3389/feart.2021.698660

Roger F Macleod, Scott R Dallimore

Open Access

https://doi.org/10.3389/feart.2021.698660

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Abstract

The southern Beaufort coastline in Canada experiences significant storm surge events that are thought to play an important role in coastal erosion and influence permafrost dynamics. Unfortunately, many of these events have not been documented with tide gauge records. In this paper, we evaluate coastal driftwood accumulations as a proxy for estimating maximum storm surge heights and the history of these events. We use historical air photos and data derived from Unoccupied Aerial Vehicle (UAV) imagery to resurvey four coastal stranded driftwood study sites that were first appraised in 1985–86 and assess two new regional sites in the Mackenzie Delta. Maximum storm surge heights were found to be similar to observations carried out in the 1980s, however, we refine the elevations with more accuracy and reference these to a vertical datum appropriate for incorporating into sea level hazard assessments. Detailed mapping, historical air photo comparisons and the UAV acquired imagery at a site close to Tuktoyaktuk demonstrate that the highest storm surge at this site (1.98 m CGVD2013) occurred in association with a severe storm in 1970. This event shifted driftwood and floated material slightly upslope from an older event thought to occur in 1944 that reached 1.85 m (CGVD2013) elevation. The quality and accuracy of the high-resolution Digital Surface Model (DSM) and orthophoto derived from Structure from Motion (SfM) processing of the UAV photographs allowed mapping of four distinct stratigraphic units within the driftwood piles. Based on variations in anthropogenic debris composition, weathering characteristics and history of movement on aerial photographs, we conclude that no storm surge events at Tuktoyaktuk have exceeded ∼1.3 m (CGVD2013) since 1970. While there has been some speculation that ongoing climate change may lead to more frequent large magnitude storm surges along the Beaufort coast, our study and available tide gauge measurements, suggest that while moderate elevation storm surges may be more frequent in the past several decades, they have not approached the magnitude of the 1970 event.

Highlights

BACKGROUNDAs recognized in many papers in this special issue on dynamic coastal permafrost systems, the effects of storm surges and associated thermomechanical degradation of ice bonded permafrost are critical processes affecting coastal erosion in the Arctic (i.e., Lim et al, 2020; Thomas et al, 2020)
The Structure from Motion (SfM) modelling produced high resolution and accurate data that were representative of the study sites providing Digital Surface Model (DSM) quality sufficient to accurately measure the maximum elevations of the ground next to the driftwood debris (Figures 4A,B)
We use Unoccupied Aerial Vehicle (UAV) and SfM methods to revisit four coastal driftwood accumulation study sites that were first appraised in 1985–86 by Harper et al (1988) and add two new sites in the Mackenzie Delta to consider if extreme storm surge magnitudes along the southern Beaufort coast are more substantive in today’s climate setting than in the past

Summary

Introduction

BACKGROUNDAs recognized in many papers in this special issue on dynamic coastal permafrost systems, the effects of storm surges and associated thermomechanical degradation of ice bonded permafrost are critical processes affecting coastal erosion in the Arctic (i.e., Lim et al, 2020; Thomas et al, 2020). In the past 30 years, the Beaufort coast has experienced warming air and water temperatures (Screen and Simmonds, 2010; Cohen et al, 2014; Graham et al, 2017), and longer and more extensive ice-free conditions (Serreze et al, 2007; Comiso et al, 2008; Overeem et al, 2011; Meredith et al, 2019) These conditions result in more extensive and longer open water conditions that can enable an increased frequency and severity of storm surges (Manson and Solomon, 2007; Vermaire et al, 2013; Greenan et al, 2018). There is only one long-standing tide station along the Canadian Beaufort coast and it has significant gaps in its recording period (Shaw et al, 1998; Manson and Solomon, 2007)

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